How to access ASP.NET applications across the firewall with some restrictions

[John]

Hi,
I have an ASP.NET intranet application running on Customer A side. Customer
B wants to access that application across the firewall. Customer A is giving
some restrictions to access the application. They are..
1. Customer B should access the application only through Port 80. No other
port will be opened on Customer A side.
2. No firewall configuration or re-configuration will be done on Customer A
side.
3. Connection should initiated by the Customer A and it will be permanent.

One Relaxation is
1. Customer A may allow outgoing connections.

I am struct with both the Architecture part and the technology part. Can you
suggest, how to go about it.

Thanks & Regards,
John